Crush-type grinding wheel truing device



L. F. POLK July 27, 1948.

CRUSH-TYPE GRINDING WHEEL TRUING DEVICE 3 Sheets-Sheet 1 Filed Nov. 20, 1944 J ATTORNEY V July 27, 1948. POLK 2,446,105

CRUSH-TYPE GRINDING WHEEL TRUING DEVICE Filed NOV. 20, 1944 5 Sheets-Sheet 2 V m 3711 111]; my "m Mimi plum mummy ATTORNEY July 27, 1948. POLK CRUSHTYPE GRINDING WHEEL TRUING DEVICE s sheeps-sheet 3 Filed Nov. 20, 1944 BY v ATTORNEY B v w d H m 3% E P & 4* l a w J3EE J QAW 3 n m Patented at 72?, 1948 CRUSH-TYPE GRINDING WHEEL TBUING DEVICE Louis F. Polk, Dayton, Ohio, aloignor to The She-meld Corporation, Dayton, Ohio. I. corporation of Ohio Application November 20, 1944. Serial No. 584,318

14 China. (01. 125-2) This invention relates to grinding machines and more particularly to means for truing or surfacingthe grinding wheel of such a machine.

One object of the invention is the provision, in a grinding machine, of a grinding wheel truing device including a rotatable crusher wheel which is carried for yielding movement on a support, together with provision for relatively moving the wheels into contact with one another, thus producing a yielding movement of the crusher wheel on its support followed by automatic locking of the crusher wheel against further yielding movement whereupon an automatic feeding movement of the wheels takes place.

Another object is the provision, in a grinding machine, of a grinding wheel truing device including a rotatable crusher wheel supported for yielding movement and so arranged that the wheels can be rapidly advanced into contact one with the other and produce yielding movement of the crusher wheel as a result of which a positive slow feeding movement of one of the wheels is initiated.

Another object is the provision of a grinding machine having a. rotatable crusher wheel for forming the grindin wheel, the crusher wheel being actuated through a yielding connection to advance the crusher wheel into engagement with the grinding wheel until a, yielding movement takes place between the crusher wheel holder and the actuator, this action being followed by an automatic adjustment of the wheels at a comparatiyely slow speed to force the wheels one into the other.

Another object is the provision of a grinding wheel of the character mentioned in which the crusher wheel holder is carried for yielding movement on an adjustable supporting slide which is positively controlled to cause rapid approach of the crusher wheel followed by a positive slow feed.

Another object is the provision of a grinding machine of the character mentioned in which the wheels are rotated at a speed substantially less than a normal grinding speed after they are brought into contact with one another and during the controlled positive feeding movement of one wheel into the other.

Other objects and advantages of the invention will be apparent from the following description, the appended claims, and the accompanying drawings, in which;

Fig. 1 is a top plan view of a crusher wheel mount embodying the present invention;

Fig. 2 is a vertical section on the line 22 of Fig. 1;

Fig. 3 is a vertical section on the line 3-3 of Fig.

g. 4 is a front elevation of the crusher wheel mount;

Fig. 5 is a perspective view illustrating the adaptation of the invention to a grinding machine in which the work is carried on centers;

Figafi illustrates the drive for the grinding wheel;

Figs, -7 and 8 are diagrammatic views respectively illustrating the electrical connections for the various operating elements, and the switch timing of the electric timing motor.

Referring more particularly to the drawings in which like parts are designated by the same numerals in the several views, it designates a grinding wheel of a grinding machine, the peripheral surface of which is adapted to be trued 0r surfaced by a rotatable crusher wheel I I, when the two wheels are pressed in surface contact and rotated at a comparatively slow speed preferably of the order of300 feet per minute. Either the crusher wheel or the grinding wheel may be positively rotated during the crushing action although in the particular form of the invention illustrated for exemplary purposes it is the grinding wheel which is positively driven by an operating motor I2. The crusher wheel is carried for free rotation on its own axis and is operated at substantially the same peripheral speed as the grinding wheel during the crushing operation through contact with the grinding wheel. A main driving motor l3 operates the grinding wheel rapidly at grinding speed during the actual grinding of the work. It will be understood that the surface formation of the crusher wheel has a contour which is complementary to the form that is to be given to the grinding wheel, and as the two wheels are rotated the grinding wheel is crushed away bit by bit until it assumes the desired shape. In the particular form of the invention illustrated the crusher wheel is provided with a series of similar annular ribs to provide ribs on the grinding wheel that may be used for grinding screw threads on the workpieces during the rotation of the workpieces. If the workpieces are reciprocated back and forth in the plane of the grinding wheel, as in a surface grinder having a reciprocal work carrying/table, the workpiece is formed by the grinding wheel to provide a surface contour similar to that/on the grinding wheel.

In accordance with the present invention, there is provision for advancing the crusher wheel and the grinding wheel into contact with one another at a comparatively rapid rate so that the wheel may be brought into engagement without loss of time even though the extent of travel may be considerable as in case of a well-worn grinding wheel. This movement preferably takes place automatically. and after the wheels come into contact there is a yielding action in the moving means as a result of which there is a locking action against continued yielding movement, and a positive slow feed at a controlled rate so that the grinding wheel and the crusher wheel will be forced slowly into one another at a speed that does not create a breaking pressure destructive of the grinding wheel. In the form of the invention illustrated it is the crusher wheel that is moved first rapidly and then at a comparatively slow feeding rate, the crusher wheel mount being supported on the grinding wheel carriage or support. That support is guided for movement on the machine base in a direction towards and from the work.

As shown more particularly in Fig. 2, the crusher wheel H is rotatably supported on a carrying shaft i4 arranged in a bracket I! having a readily movable end plate It which permits convenient assemblage of the parts. The bracket II is secured by fastening bolts H on a holder it which is slidably guided on a holder support 20 arranged on a housing It for movement of the crusher wheel toward and from the grinding wheel. The direction of movement of the crusher may coincide with a line radial of the grinding wheel or may be along a line parallel to and displaced from such a radius.

The holder I8 is grooved at 2| to receive 0116-. half of the holder support 20 which consists of a two-piece slide having plate portions 23 fixed together. One of these plate portions is in sliding engagement with the holder i8 and the other is slidably guided in a groove 24 in the housing l9.

Fixed to the holder support 20 is an internally threaded boss 21 which is operable along a threaded adjusting shaft 28. The latter is suitably mounted for rotation in a bearing 29 at its upper end and a bearing 30 at its lower end, the upper end of the shaft projecting up through the cover plate 3i and having a square operating end 32 by means of which it can be manually turned. Rotational movement of the shaft 28 thus causes up or down travel of the support 20 (see Fig. 2), and if at that time this slide is fixed to the holder l8 a corresponding movement of the holder ill will take place on the housing l9. However, at times, the parts it and 20 are not fixed together, and yielding movement of the holder i8 can take place on the support 20. A spring 34 interposed between a projection 35 at the lower end of holder l8 and the lower end of the slide or support 20 normally acts to yieldingly maintain the holder ID in a lowered position with respect to the support 20.

The supporting slide 20 is provided with a horizontal groove 36 receiving a pin 31 on the end of a lever 38 which is arranged in a recess in the support 20 and is pivoted on the holder l8 by a short shaft 38. The axis of the shaft 39 is horizontally displaced from the pin 31 as will be apparent from Fig. 4 which indicates the normal position of the holder It with the crusher wheel out of contact with the grinding wheel and the spring 34 yieldingly keeping the holder i8 in a lowered position. When the support 20 is lowered by operation of the screw 28 until the crusher wheel contacts the grinding wheel and a resistance to further movement is imposed on the crusher wheel, the crusher wheel holder is remains stationary and the continued lowering of the support 24 compresses the spring 24. This relative motion of the holder II. and support 20 causes the lever 24 to swing counterclockwise as viewed in Fig. 4 and as soon as it has turned a little distance. it moves away from and closes a limit switch 4| (see Fig. 4). The limit switch is so connected as to operate a solenoid 4i so that the solenoid plunger 42 travels upwardly and straightens a toggle linkage 43. This action moves a locking finger- 44 into pressure contact with 'the lever It. preventing further rotation of this lever and thus serving to lock or fix the holder is to the support 24.. This secures the holder against further movement on the holder support 20 and then it will be apparentthat continued rotation of the shaft 28 will cause positive movement or the crusher wheel toward the grinding wheel. It should also be noted that the movement of the crusher wheel toward the grinding wheel may take place through whatever spacing may exist between the two wheels until the crusher wheel engages the grinding wheel. the subsequent locking of the holder to the holder support then taking place automatically and affording firm engagement of the wheels under positive control.

After the wheels are brought into engagement with one another and as a result of the relative motion of the crusher holder onthe crusher support, slow speed rotation of the grinding wheel is initiated. The wheels are brought into contact with one another while the grinding wheel is stationary and the main drive motor I2 is disconnected or tie-energized. Excessive wear at localized points on the crusher wheel is thus prevented. After the crusher wheel contacts the grinding wheel, as previously mentioned, the operating motor I2 is energized and also the comparatively rapid rotation of the shaft 28 that takes place during rapid advance of the crusher wheel is automatically changed to a comparatively slow feeding rate. which continues through a predetermined interval of time or through a predetermined number of revolutions of the grinding wheel suflicient to give an adequate truing action on the grinding wheel. Further feeding movement of the crusher wheel is then automatically stopped during the continued rotation of the grinding wheel for two or three turns or so and while the holder I8 is secured to the holder support 20 and held in a fixed position so that a truly concentric form will be imparted to the grinding wheel. There is then an automatic reversal in the direction of the operation of the shaft 28 to produce a rapid withdrawal of the crusher wheel, and during at least the first part of this withdrawal the crusher wheel holder II is secured by the locking finger 44 to the support 20. This retracting movement of the shaft 2| continuesuntil the holder It returns to its normal raised position shown in Fig. 2 and then the aligned arm arrangement of the toggle linkage 43 is broken by a controlling pin 46 which is brought up into engagement with the stop bar 41 fixed on the housing IS. the solenoid 4i being deenergized at this time. The finger 44 is thus withdrawn and the holder is is released from Referring again to Fig. 2, it will be noted that the housing I8 carries a variable speed adjusting motor 48 having a geared connection through the gears 58 and.5| to a gear 52 fixed to a clutch plate 58 which is free on the shaft 28. A clutch hub 54 splined or keyed to the shaft 28 may be operated int yengagement with the clutch plate 83 to provide an operating connection between the shaft 28 and the motor 48 to turn the shaft 28 comparatively rapidly in one direction or the other, depending upon the direction of rotation of the motor. Gear is arranged on a shaft 85 provided with a worm 56 meshing with the worm wheel 51 on shaft 58. Fixed on the shaft 58 is a worm engaging worm wheel 88 which is free on the lower end of shaft 28. The worm wheel 88 is provided with a clutch plate 8| which may be engaged by the clutch hub 54 when thelatter is lowered. The transmission mechanism just described operates the shaft 28 at a comparatively low rate of speed to lower the support 28 and thus slowly lower the crusher wheel into the grinding wheel during the truing action that takes place with these wheels rotating slowly in firm contact with one another. In this operation the speed of the motor 48 is adjusted in accordance with the grinding wheel size and construction to prevent excessive pressure between the crusher and the grinding wheel.

The clutch hub 54 is controlled automatically as by means of a control arm 82 having a lifting roller 82 engaging an operating cam 84. A lowering roller 85 is also provided on the arm 82, en-

gaging a complementary lowering cam 86 (see Fig. 3). The cam 64 is provided'with suitable recesses and camming surfaces to operate the clutch hub into engagement with the clutch plate 88 or ii or to a position between those plates The cam 84 is fixed to a ratchet wheel 81 controlled by a ratchet pawl 68 on a lever 88 which,

out of the path of the crusher wheel. As shown r in Fig. 4. the cover housing II is provided with two slidable cover sections 12 and 18 which are movable laterally away from one another and away from a location below the crusher wheel. Thus the cover section I2 may be moved to the left as viewed in Fig. 4 into the dotted position, while the other cover section I8 is moved correspondingly to the right. This movement may be provided by a suitable linkage including link 14 pivotally mountedat 15 on the main portion of the grinding wheelhousing. Arms 18 are connected to these links 14 and to an operating stud 'Il which is slldably guided in a groove 18 in the grinding wheel housing. The stud 11 is provided on the armature 18 of solenoid 88 so that when the solenoid is energized the arms 18 will be raised and spread, moving the sections 12 and 13 outwardly. The solenoid 88 is energized automatically at the time of initiation of the crushing cycle. After the crusher wheel holder is raised to retracted position, the solenoid 88 is deenergized and the cover sections 12 and 13 are returned by spring 8|. When the crushing cycle is completed the grinding wheel may be traversed as required to properly engage the work and the grinding operation performed by operating the grinding wheel at normal grinding speed by-the driving motor II. An overrunning clutch 88 permits high speed operation of the grinding wheel without driving the operating motor |-2.

An adjustment is provided for properly positioning the axis of the crusher wheel H with respect to the axis of the grinding wheel. For this purpose the bracket I5 is adjustably supported on the holder l8 for movement about a line tangent to the crusher wheel and midway between the ends of the crusher wheel where it engages the grinding wheel. The axes of the grinding wheel and the crusher wheel may thus be arranged in exact parallelism or slightly out of 'a true parallel condition to compensate for deflections that might take place in the shafts or bearings of either one of these wheels during the crushing operation. The bolt holes which receives'the holding bolts l1 are arranged in the bracket II in a concentric arrangement with respect to this axis of adjustment just mentioned and the bolts l1 pass through arcuate slots provided in the'wall portions 88 of the holder l8 where the holder extends down at the sides of the bracket I 5.

Fig. 7 shows the various electrical connections of the apparatus. The motor l3 for driving the grinding wheel during the grinding operation at a/suitabie normal grinding speed is connected to a three-phase supply source 88 through a switch a. This supply source is also connected through switch b to the operating motor 2 which turns the grinding wheel at a reduced speed in the crushing operation, although it should be understood that'a single motor can be used in place of the two motors I2 and I3 if suitable speed variation is provided. The reversible adjusting motor 48 is supplied either through a switch c or a switch d depending upon the direction of rotation desired. The-switch e connects the source of power to the solenoid 88 which, when energized, moves the cover sections 12 and 13 out of the path of the crusher wheel. Switch b| controls the energization of the solenoid 4| which governs the locking of the crusher holder to the crusher supporting slide 28. Switch 1' connects to the.

coolant fluid in the crushing operation.

One phase of the supply line is connected across the primary of a transformer 88 having a secondary which is connected to the lead lines 88 and 8|. The dead line 8| is connected to one side of switch controlling relays A, B, C, D. E and F, which respectively control the operation of the switches a, b, c, d, e and f. The lead line '88 connects through a start switch 92 which is normally open, a normally closed stop switch -88, normally closed relay control switch e| to the motor controlling relay winding A so that when the start switch 82 is closed, the grinding wheel motor I8 will be energized during the grinding operation. The relay coil-A closes a switch al to complete a holding circuit about the start switch 82.

The lead line 88 is connected to the switch controlling relay E by a start switch 94 and a normally closed stop switch 85. Although the op.- erator would normally stop the main grinding wheel motor l3 by operating the stop switch 82 before starting a crushing cycle of operations,

7 the decnergization of the motor It is insured by the switch eI which is opened when the relay E is energized. The energization of the relay E closes the switch e to retract the wheel guard cover sections. When the relay E is energized, it also closesa holding circuit switch e2 which is connected through normally closed limit switch ll around the start switch I. This limit switch It is momentarily opened by the toggle links ll as the toggle links move from their straightened position to the angular position shown. As the limit switch I isclosed except when the toggle,

links move to an angular position at the end of a crushing cycle. the holding circuit will be maintained around the start switch 04 until the crusher holder has been moved up to a raised position, elevating the crusher above the wheel guard position. The opening of the switch 98 at that time will automatically interrupt the current iiow to the relay winding E at the end of a crushing cycle.

When the relay winding E is energized, it closes another switch at which is connected through a microswitch 88 which is normally closed, a normally closed switch dI (which is opened when the relay coil D is energized), and a cam controlled switch I! to the relay winding C. The microswitch II is prot 'led as a safety factor and is only opened in case of excessive movements of the lever 38 in a counterclockwise direction as viewed in Fig. 4. The automatically controlled switch 09 is closed and the cam Hill which controls it is stationary at the time. This cam is provided on a cam shaft which constitutes a timing mechanism. the cam shaft being driven by a small timing motor IIII which, when energized, operates the cam shaft through one revolution in a predetermined time interval and then stops. Fig. -8 shows the timing of the switchesoperated by the various cams on the shaft of this motor IIII, The energization of the relay C closes the switch 0 so that the adjusting motor 49 will start operating and rapidly move the crusher holder downwardly since the clutch controlling arm 62 will be raised at the time, holding the clutch hub 54 in engagement with the upper clutch disc Ill as diagrammatically shown in this figure. When the relay coil 0 is energized it also closes the switch cl to start the coolant flow to the crusher so that coolant is supplied to the grinding wheel all during the down movement of the crusher.

The downward movement of the crusher holder will continue at a comparatively rapid rate until the crusher engages the grinding wheel and the yielding action takes place between the holder II and the plate portion 23. As one portion of lever ll is connected to the holder Il and another portion operates in the horizontal groove in plate 23. see Figs. 2 and 4, the lever ll swings counterclockwise and permits closure of the limit switch ll which is normally held open by the lever 88. As soon as the switch closes it completes a circuit through a switch d2, through a cam operated switch I03 closed at this time. to the relay coil F. which then immediately closes switch I energizing solenoid I0 and moving the ratchet wheel '1 to turn the cam 64 through one step which serves to lower the arm 62, disengaging clutch face 53 and engaging the lower clutch face II so that the shaft 28 will continue its rotation in the same direction but at a greatly reduced speed. The lowering of the clutch disc closes a limit switch I as soon as full engagement takes place with the lower clutch face II. The clutch hub I4 is carried for yielding movement on the arm 6! by means of springs ll interposed between lugs on that arm and slide members It that carries the clutch hub so that the two clutch parts may properly position themselves with the teeth of one opposite the spaces on the other. when the switch I closes a connection is made through lead line III to the motor III. starting this motor and causing the rotation of the shaft that operates the cams I" controlling switch I03. cam I" controlling switch SI, two additional cams I01 and I" controlling switches I 09 and H0 -respectively. and a cam II! which closes a holding circuit through a switch Ill by means of which the motor IIII is stopped after one revolution of the cam shaft. At the same time the microswitch I is closed, that is, after the crusher has engaged the grinding wheel and the arm- 38 closes switch I. as previously mentioned. switch I04 being closed at the time, a circuit is completed through the relay coil B through the cam operated switch I09 closed at this time. The'energization of the relay coil B closes a holding switch b2 around the microswitch IM. It also closes switch b to start the grinding wheel operating motor I! to drive the grinding wheel at crushing speed. At the same time the energization of relay coil B also closes switch bI to energize the solenoid I and lock the crusher holder to its supporting slide. 7

. After a predetermined time interval dependent upon the amount of time required for a crushing operation and preset in accordance with the particular grinding wheel characteristics, switch 99 will be automatically opened, deenergizing the relay 0 and thus causing the switch c to open so that the motor 49 will be deenergized. The downward movement of the crusher is thus stopped although the operating motor I! continues to rotate and any eccentricities in the surface of the grinding wheel are removed during a few revolutions of the grinding wheel. At the time switch 89. opens, the cam controlled switch III is closed again to energize solenoid I0 and move the ratchet controlled cam plate 04 through another step in which the clutch hub 54 is moved to a neutral .posltion. After a short time interval sufllcient for a few revolutions of the grinding wheel without further feed of the crusher the cam III'I opens switch I", deenergizing relay B to open the switch supplying the motor I2. and also open the switch bl and deenergize the solenoid 4| so that the lock between the crusher holder and its supporting slide can be subsequently released when the crusher holder is fully retracted. After the deenergization of the motor I2 another energization of the sole- -noid In takes place through the cameontrolled switch I, moving the clutch hub up into engagement with the clutch face 53 so that the shaft 2! will be rapidly rotated in a direction to raise the crusher holder after the motor 49 is energized. The motor 48 is now energized by the cam controlled switch IIII, energizing the relay D. Energization of the relay coil D also closes the normally open switch d3 providing a holding circuit so that the up travel of the crusher holder continues until the switch e3 opens. Switch e! is opened by the deenergization of the relay coil E when the limit switch 96 is temporarily open circuited by the movement of the toggle arms into an angular position when the crusher holder is fully retracted. As soon asthe relay coil E is deenergized, the various circuits are interrupted and the parts are then again in the starting position ready for another cycle.

supply to the solenoid controlling coil 1' preventing further indexing operation of the ratchet plate until the next cycle. Shortly after the ,switch llll closed to start the up feed drive of the motor 49, a full revolution of the cam shaft is completed and switch I I automatically broken to stop further operation of motor "ll. At the time of deenerglzation of the relay coil E at the end of the crushing cycle, the switch e is opened again, deenergizing the solenoid 80 and causing the return of the cover guard sections 01' the grinding wheel housing. At the time the relay coil C was deenergized, at the end of the down feed movement, the switch cl which it controls is opened and the coolant supply to the crusher is stopped. 1

While the form of apparatus herein described constitutes a preferred embodiment of the invention, his to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a power operated actuator having a yielding connection to said holder, means for moving said actuator to advance said crusher wheel into engagement with said grinding wheel and then cause relative yielding action between the holder and the actuator, means automatically operable as a result or such yielding movement for locking the holder to the actuator, and means for automatically adjusting one of said wheels positively at comparatively slow speed after said locking action to force said wheels one into the other.

2. A grinding machine having a, rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, 'a power operated actuator slidably supported on said grinding wheel support and slidably supporting said crusher wheel holder, said actuator having a yielding connection to said holder normally maintaining said holder in a predetermined position, means for moving said actuator to advance said crusher wheel into engagement with said grinding wheel and then cause relative yielding action between the holder and the actuator, means automatically operable as a result of such yielding movement for locking the holder to the actuator, and means for automatically adjusting one of said wheels positively after said locking action to force said wheels one into the other.

3. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a power operated actuator having a yielding connection to said holder, means for moving said actuator to advance said crusher wheel into engagement with said grinding wheel ancLthen cause relative yielding action between the holder and the actuator, power means for driving one of said wheels at a, peripheral speed less than the normal grinding speed of the grinding wheel, means automatically operable as a result or such yielding movement for locking the holder to the actuator and initiating operation of said power means, and meansior automatically adjusting one of said wheels positively at comparatively slow speed after. said locking action to force said wheels one into the other.

4. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, guard means between said wheels, a power operated actuator having a yielding connection to said holder, means for removing said guard means and for moving said actuator to advance said crusher wheel into en-- gagement with said grinding wheel and then cause relative yielding action between the holder and the actuator, means automatically operable as a result of such yielding movement for looking the holder to the actuator, and means for automatically adjusting one of said wheels positively at comparatively slow speed after said locking action to forcesaid wheels one intothe other.

5. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a power operated actuator slidably supported on said grinding wheel support and slidably supporting said crusher wheel holder, said actuator having a yielding connection to said holder normally maintaining said holder in a predetermined position, means for moving said actuator to advance said crusher wheel into engagement with said grinding wheel and then cause relative yielding action between the holder and the actuator, power means for driving one of said wheels at a peripheral speed less than the normal grinding speed of the grind ing wheel, means automatically operable as a result of such yielding movement for locking the holder to the actuator and initiating operation of said power means, and means for automatically adjusting one of said wheels positively at a comparatively slow speed after said locking ction to force said wheels one into the other.

6. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a retatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a holder support on which said holder is mounted for yielding movement in a direction towards and from the grinding wheel, means for moving one of said supports to cause engagement of said wheels and yielding movement of said holder on the holder support, means forautomatically locking said holder to the holder support subsequent to engagement of said wheels. and means for automatically moving said holder support at comparatively slow speed to cause further approach of the pressure wheel and the grinding wheel axes.

7. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a holder support on which said holder is mounted for yielding movement in a direction towards and from the grinding wheel,

power means for positively moving one of said supports at a substantially constant rate of advance to cause engagement of said wheels and yielding movement of said holder on the holder support, and means for automatically adjusting one of said supports at comparatively slow speed with a substantially constant rate of advance to force said wheels one into the other.

8. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a romeans for moving one 01' said supports to cause engagement of said wheels and yielding movement oi said holder on the holder support, means for automatically locking said holder to the holder support subsequent to engagement of said wheels,

and means for automatically adjusting one or said supports at comparatively slow speed after said holder is locked to the holder supportto force said wheels one into the other.

9. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a' rotatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a holder support on which said holder is mounted for yielding movement in a direction towards and from the grinding wheel, means for positively moving said holder support at a rapid rate to cause engagement of said wheels and yielding movement of said holder on the holder support, means, for automatically locking said holder to the holder support subsequent to engagement of said wheels. and means for automatically adjusting said holder support at comparatively slow speed after said holder is locked to the holder support to force said wheels one into the other.

10. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a crusher wheel bracket carrying said crusher wheel for rotation about its own axis, a holder for said bracket on which said bracket is adjustably mounted for adjustment or the angular relation of the axes of said wheels, a power operated actuator. means for moving said actuator to advance said crusher wheel at a substantially constant rate or advance into engagement with said grinding wheel, and means for automatically adjusting one of said wheels to force said wheels one into the other.

11. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, a'crusher wheel bracket carrying said crusher wheel for rotation about its own axis, a holder for said bracket on which said bracket is adjustably mounted for adjustment of the angular relation of the axes of said wheels, a power operated actuator having a yielding connection to said holder, means for moving said actuator to advance said crusher wheel into engagement with said grinding wheel and then cause relative yielding action between the holder and the actuator, means for locking the holder to the actuator, and means for automatically adjusting one of said wheels positively at comparatively 12 slow speed to force said wheels one into the other.

12. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a rotatable crusher wheel for forming the grinding wheel, power means for slowly rotating said grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a holder support on which said holder is mounted io'rmovement in a direction towards and from the grinding wheel, means for moving said holder support at a comparatively rapid rate to cause engagement oi said wheels. means for automatically locking said holder to the holder support subsequent to engagement of said wheels and for initiating operation of said power means, and means for automatically adjusting one of said supports at comparatively slow speed after said holder is locked to the holder support to. force said wheels one into the other.

13. A grinding machine having a rotatable grinding wheel, a grinding wheel support, a r0- tatable crusher wheel for forming the grinding wheel, a crusher wheel holder rotatably supporting said crusher wheel, a holder support on which said holder is mounted for yielding movement in a direction towards and from the grinding wheel, screw means for moving said holder support to cause engagement of said wheels and yielding movement of said holder on the holder support,

means for automatically locking said holder to the holder support subsequent to engagement of said wheels, and means for automatically adjusting said screw means at comparatively slow speed after said holder is locked to the holder support to force said wheels one into the other. 14. A grinding machine having a rotatable grinding wheel, a grinding wheel support,a ropower mechanism for moving said crusher wheel holder to move the crusher wheel towards and from the grinding wheel at a substantially con.- stant rate of advance, power mechanism for antomatically feeding one of said supports at a substantially constant rate of advance to cause unanimous crran The following references are of record in the file of this patent:

FOREIGN PATENTS Country Date Great Britain Mar. 15, 1940 Number 

